History


The Story of the 69-Inch Mirror Move

Photo by Jim Gauldin

The mirror above was the
FIRST LARGE TELESCOPE MIRROR EVER CAST IN THE WESTERN HEMISPHERE!
In 1931, it was the third largest in the world!

You may want to first read the History of Perkins Observatory for context on this story.

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Chapter 1 : Creation of the Mirror

In which we discuss how the mirror came to be.

Prior to 1923, if you wanted a big mirror for your telescope, you went to Europe. All the glass making factories of any importance were located there. But at the time he made his gift to the Ohio Wesleyan University, Hiram had stipulated that the mirror be made in America. In any event, since this was right after World War I, most European glassworks were in ruins.

 

The task eventually fell to the U.S. Bureau of standards to cast the large mirror blank. It may seem odd that an organization created to standardize weights and measures would try its hand at mirror-making. The idea was that once they understood the techniques involved, this information would be passed on to private companies. From that point on, the United States would no longer be dependent on Europe for its telescope mirrors.

 

The first four attempts to cast a mirror blank were unsuccessful. The cooling process is the most critical part of mirror-making, and it is here that they encountered the most difficulties. After the glass pieces melted and flowed into the mold, the oven had to be cooled very, very slowly to avoid stress in the glass that can occur if parts of it are different temperatures. On the fifth attempt the glass blank was cooled so slowly that it took almost eight months before it could be removed from the oven.

Here is G. K. Burgess (right), Director of the Bureau of Standards at the time, and C. C. Crump, first Director of Perkins Observatory. Mr. Burgess is pointing out the 8-inch hole bored through the mirror blank. The core removed from the hole sits on top of the mirror.

And still the mirror was not finished. Having a 69-inch blank is all well and good, but it needed to be ground to the proper shape and polished to perfection. This took an additional three years. When it was finished, it was the first large telescope mirror ever made in the United States, or, for that matter, in the entire Western hemisphere!

At 69-inches wide and 9.5 inches thick, the mirror weighs in at about 4,000 pounds. almost two tons of glass! At the time, it was the third largest telescope mirror in the entire world!

The 69-inch mirror was installed at last in 1931, eight years after construction of the observatory began.

Chapter 2: Use of the Mirror

The incredible Eye on the Sky!

For 30 years, the 69-inch telescope resided at Perkins Observatory. It was used primarily for spectroscopic work.

However, Ohio is really not a great place for a large research instrument. The generally crappy weather and low elevation combine to limit the amount of useful data that can be collected from a telescope. Even worse, after World War II, the use of outdoor nighttime lighting increased dramatically throughout the urban areas of America. As a result, light pollution has robbed most people of their ability to enjoy the stars. It clearly robbed the Perkins Telescope of its usefulness

Chapter 3: the Amazing Mirror Road Trip!

How much fun should one telescope mirror be allowed to have, anyway?

In1961 the decision was made to move the Perkins Telescope to Lowell Observatory in Flagstaff, Arizona. This was done to provide darker skies, fewer clouds, and a higher elevation. This was the largest telescope to ever be moved, before or since.

The move was paid for with a grant from the National Science Foundation. Remember, in the 1950's and 60's the United States was charging full speed ahead in the "Space Race". Science education was the cause of the day, and the NSF had more money than they seemed to know what to do with.

Once the telescope was moved and reassembled, the 69-inch mirror stayed in use for just a couple of years. In 1932, just one year after the mirror was finished, Dow-Corning introduced a new glass-like material called "Pyrex". Because of its very low coefficient of expansion, Pyrex was ideal for use in cooking, baking, and telescope making. Since Pyrex mirrors are so much better than crown-glass mirrors (like the 69-inch), a new mirror was cast for the Perkins Telescope. As it turns out, the new mirror was 72-inches across.

But the 69-inch didn't stay in Arizona for long. In 1964 a new science museum opened in Columbus, called COSI (the Center of Science and Industry). Two of the high-ranking staff members thought that the mirror would make an excellent exhibit, and arranged for its extended loan from the Ohio Wesleyan University. They then rented a truck and drove to Arizona to pick it up. On the way back, they managed to burn out all of the gears in the truck except for one - first gear. So the 69-inch mirror came back to Ohio from Arizona, all the way, in first gear.

The mirror stayed at COSI for 35 years. For most of that time it was on display on the second floor in the Earth Sciences Area. At one time, COSI designed a very nice series of exhibits on glass and optics with the mirror as its centerpiece. However, in the late 1980's they decided to take it off display. They didn't move it into storage (4,000 pounds, remember?). Instead, a closet was built around it.

Chapter 4: Return of the Mirror!

At long last, our baby comes home.

On Tuesday, September 14th, 1999, the 69-inch mirror came home to Perkins Observatory. Removal of the mirror from the wall took place the day before. It was brought down a newly-installed freight elevator and crated up in the first floor exhibit area in preparation for loading and hauling to Perkins the next day.

 

photo by Bob Martino

photo by Gary McCool

photo by Mike Godwin

Here you can see the mirror in the closet, recessed into the back wall. It looks like there is a quarter slice taken out of it. Actually, COSI covered three quarters of the mirror with aluminized mylar. This was to show what it looked like when it was in use. Part of it was left uncoated so that visitors could see into the glass itself. In its day this was actually a very nice exhibit. Note that in the center photo you can see the reflection of the rest of the closet and its contents.

The closet doors and part of the wall had to be torn out in order to remove the mirror. Gary McCool and Bob Martino also attacked the alcove where it once rested with sledgehammers and crowbars. We really needed the wooden cradle that the mirror rested on (seen in right photo, sitting upside-down). In the end, we took the cradle and most of the alcove as well.


photo by Bob Marino

photo by Mike Godwin

photo by Mike Godwin

After bringing it down from the second floor, the COSI folks built a crate specifically to ship the mirror. The next day was moving day. Here we see it being loaded onto the truck. Many Perkins volunteers and CAS (Columbus Astronomical Society) members were on hand for the historic occasion.

photo by Jim Gauldin

The local media(Channel 10) interviews Don Stevens, Perkins Observatory volunteer(Now staff member).

 

photo by Jim Gauldin
The truck with the crated mirror arrives at Perkins Observatory (left).

The truck backs up to the rear entrance of Perkins (right).

photo by Mike Godwin

photo by Mike Godwin

photo by Mike Godwin

photo by Mike Godwin

photo by Mike Godwin
The unwrapping and uncrating ceremony had everyone choked up. It was the first time in 35 years that the mirror had seen the light of day.
photo by Mike Godwin
  WHOO-HOO!  
 

After a quick wipe-down with Windex to clean the sawdust away, Jim Gauldin (bottom right) attempts to use the 69-inch as a solar cooker. However, since it has about an f-7 focal length, Jimmy really needs a 40-foot long stick!

NOTE! Do NOT attempt this with your telescope mirror at home! Windex and hotdog grease have been known to degrade the performance of most astronomical optics! The mylar on the mirror is just for show, and will be stripped off at a future date anyway.

photo by Jim Gauldin

Perkins Director Tom Burns is the center of attention as he is interviewed by two local television stations at once. The story went out on local channels 10 and 4, as well as the Ohio News Network. CAS members also film the cameramen filming Tom. Jim Gauldin took this picture of the CAS members taking pictures of the news people taking pictures of Tom. Sorry, but we did not get a picture of Jim taking this picture of the CAS members taking pictures of the news people taking pictures of Tom.


photo by Gary McCool

photo by Gary McCool

photo by Mike Godwin

photo by Bob Martino

photo by Bob Martino

photo by Bob Martino

And so the 69-inch mirror creeps - slowly - up to the back door of Perkins...

It is sometimes said that with any job, 90% of the work takes 10% of the time, and the final 10% of the work takes 90% of the time. This seemed to be the case with the mirror move. We were not at all certain at the start of the project exactly HOW that mirror was going to get through the back door and into Perkins. Fortunately, the experts at Wanner Metal Worx knew what they were doing.


photo by Jim Gauldin

photo by Mike Godwin

photo by Bob Martino

photo by Bob Martino
Removing the doors. There was exactly 71 inches of clearance with the doors gone. Since the forklift wouldn't fit through the door, the last couple of feet required creative thinking. The 69-inch is lowered onto a padded dolly... ... And the first large telescope mirror ever made in the United States is brought home at last!

The 69-Inch Perkins Mirror is now on display at Perkins Observatory. If you would like to see it, why not come out for one of our public programs? And bring the kids!

Perkins Observatory would like to thank COSI. Not only did they return our mirror with very little fuss, but they also gave us several pieces of equipment and exhibit cases which they no longer had a use for. We wish them great success in their new location.

We would especially like to thank the generous, professional folks at Wanner Metal Worx of Delaware for providing the truck, forklift, warm bodies, and expertise necessary to get the mirror from the loading dock at COSI up the road and into Perkins Observatory once again. This would have all been impossible without their help. Take a bow, fellas!

photo by Mike Godwin

Currently, Perkins is in a state of flux. We are expanding our public programs, building exhibits, and trying to make the observatory a great place for the public to learn all about Astronomy and Space Exploration. We have opened a playroom for our younger guests, an exhibit area where you can learn a lot about astronomy and the observatory's history, and a gift shop where you can find educational toys, books, telescopes, posters, and much more!

 

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